wifi: Fixing Nits

Changes in the CL to fix bugs found while integrating
with framework:
1. Added IWifiApIface.setCountryCode()
Bug: 34682168
2. Fixed documentation nits in .hal files.
Bug: 34468218
3. Changed roaming state enum values.
Bug: 34715231
4. Added log for EBUSY in legacyErrorToString()
Bug: 34715469
5. Remove "-Wno-unused parameter" from Android.mk
Bug: 34611289
6. Remove the erroneous |onFailure| callback invocation in wifi.cpp.
7. Add null terminations to strings passed to legacy HAL API's
8. Remove unused |IWifiStaIface.stopDebugPacketFateMonitoring|.

Test: Compiles
Change-Id: If3a3e2f360a378c59dc56b8bbe3a0c6d400b3bd8
diff --git a/wifi/1.0/IWifiApIface.hal b/wifi/1.0/IWifiApIface.hal
index 6bc3580..aeca2cd 100644
--- a/wifi/1.0/IWifiApIface.hal
+++ b/wifi/1.0/IWifiApIface.hal
@@ -22,5 +22,15 @@
  * Interface used to represent a single AP iface.
  */
 interface IWifiApIface extends IWifiIface {
-  /** TODO(rpius): Add methods to the interface. */
+  /**
+   * Set country code for this iface.
+   *
+   * @param code 2 byte country code (as defined in ISO 3166) to set.
+   * @return status Status of the operation.
+   *         Possible status codes:
+   *         |WifiStatusCode.SUCCESS|,
+   *         |WifiStatusCode.FAILURE_UNKNOWN|,
+   *         |WifiStatusCode.FAILURE_IFACE_INVALID|
+   */
+  setCountryCode(int8_t[2] code) generates (WifiStatus status);
 };